Smoke rises from crippled Japan nuke plant

Japanese foods make up less than 4 percent of all U.S. imports, and the FDA has said it expects no risk to the U.S. food supply from radiation.

Residents of cities in Japan's northeast had been advised not to drink tap water due to elevated levels of radioactive iodine.

However, in Tokyo, the radiation found in Tokyo tap water measured just 2.9 becquerels as recently as Sunday, according to government reports. The Tokyo Water Bureau is the main source for tap water for the city.

Babies in Tokyo should not be fed tap water long-term but can be bathed in it, officials said.

"Even if a baby drinks this water several times, it will not cause health troubles," said Hasumi Nishiya, an official at water safety division at the Tokyo Metropolitan government.

Experts also say iodine-131 dissipates quickly in the air, with half of it disappearing every eight day